REFLECTOR: Intercom Noise

[aminetech at bluefrog.com]

A while back I reported that I found a bad ground and eliminated the intercom noise. After 20 hours of quiet operation, the noise is starting to return. It's infrequent and not to annoying, but I don't want it to get worse. I've attahced a pic of the barrier strip where I found the bad ground. (I'm sending the pic of the left side separately). My plane was built with a second battery and I believe this barrier strip was part of the backup system. The backup battery and alternator were removed before I bought the plane, so I'm not sure.  Here is what I know.

Terminal B is the EI mag wire.  It goes to the mag switch and the circuit returns through the shield and terminates at terminal C which appears to be grounded to the firewall.

Terminal 1 is the power wire going to the EI.  With the EI mag switch up, B is grounded and 1 has 11.8 v.  With the mag switch down, B is not grounded and 1 has no voltage.  Is this how EI s are normally wired?  I figured the mag switch would simply cut off the power.

Terminal 8 has 2 wires.  One is power from the master.  I don’t know where the other wire goes.  It reads 12.4 v with the master on.

The terminal 2 wire goes to the EI ground.  I need to check where it is grounded to.

Terminals 8 and 9 are connected and read 11.8 v when the EI mag is on and the voltage goes up to 12.4 v with the EI mag off.



Terminal 3 is the bad ground, and 4 is a mounting screw that is also grounded to the #3 wire. I didn't replace anything, just removed #3 and 4 and put back on. Before I removed them, the #3 screw was reading 5-900 ohms, now it is 0. With both 3 and 4 removed, the EI did not operate. With 4 connected the EI ran, but rough at low rpm. With 3 also connected it ran fine.

I would appreciate anything anyone can tell me about all this.  If there is something that I can remove, I would like to do so.

John
-------------- next part --------------
A non-text attachment was scrubbed...
Name: barrier strip 2 a.jpg
Type: image/pjpeg
Size: 147050 bytes
Desc: not available
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20110308/376d7069/attachment-0001.bin>